One cylinder two cycle engine



y 6, 1958 E. G.- MAYNARD k 2,833,256

ONE CYLINDER TWO CYCLE ENGINE Filed Jan. 31, 1957 24 .25 0 I 24 Fig.1. 2 Fig.2.

INVENTOR. ERNEST QMA YNARD BY 72W)? Y PM AT 1' ORNEYS impeller as in U. S. Patent United States Patent 2,833,256 ONE CYLINDER TWO CYCLE ENGINE Ernest G. Maynard, Nashua, N. H. Application January 31, 1957, Serial No. 637,489 7 Claims. (Cl. 12373) This invention relates to one cylinder, two cycle, in ternal combustion engines and particularly to miniature engines much used on model airplanes, boats and automobiles. i

In the prior art such engines have sometimes been provided with hollow crankshafts, the crankshaft bore leading into the crankcase compression chamber and the shaft having an aperture in a peripheral wall for periodically connecting with a fuel intake conduit. The fuel has thus been directed into the base of the compression chamber at the level of the crank shaft axis and then has been redirected up to the combustion cylinder usually in a conduit extending along the sides of the cylinder. The hollow shaft increases the volume of the compression chamber and tends to reduce the volumetric efficiency of the engine. Such a hollow shaft valve arrangement is shown in U. S. Patent No. 2,733,694 to Brebeck of February 7, 1956. 7

It has also been proposed to provide a solid shaft having an impeller and a hollow sleeve valve attached to the No. 2,547,327 to King of April 3, 1951. The shaft itself does not serve as the valve means but indirectly rotates an encircling hollow sleeve having a valve aperture. The hollow sleeve increases the volume of the compression chamber, in the same manner as a hollow shaft and therefore also tends to reduce the volumetric efficiency of the engine.

The principal object of this invention is to increase the eiiiciency of miniature, two cycle, engines by reducing displacement at the base of the crankcase compression chamber, increasing displacement in the fuel feed conduit to the. cylinder and to achieve a direct, shortflow of fuel from the'fuel intake conduit through the fuel feed conduit and into the cylinder.

Another object of the invention is to provide improved rotary valve means in miniature two cycle engines wherein a solid, cylindrical crank shaft serves as a rotary valve plug for connecting the fuel intake port with the fuel feed conduit of the engine.

A further object of the invention is to increase the volume of fuel feed to a miniature two cycle engine by grooving a solid crankshaft rather than perforating a hollow crank shaft thereby increasing the area of cross section of the fuel passage by the thickness of one quadrantal wall of a hollow shaft.

Still another object of the invention is to provide fuel ports, passages and conduits in a miniature two cycle engine of increased area of cross section terminating in an inlet port on the frontof the cylinder nearly equal in width to one third the circumference thereof and to pro vide dual exhaust ports on the sides and rear of the cylinder, each nearly equal in width to one third said circumference and greater in joint total area than the area of said inlet port.

A still further object of the invention is to provide a straight, elongated, groove having an arcuate bottom intermediate of a solid crank shaft for serving as a valve "ice port or passage, in a miniature two cycle, single cylinder engine.

Other objects and advantages of the invention will be apparent from the claims, the description of the drawing and from the drawing in which a preferred embodiment is illustrated.

Fig. 1 is a side view in section of an engine according to the invention, showing the piston and valve means during the fuel intake portion of the stroke.

Fig. 2 is a view similar to Fig. 1 showing the combustion portion of the stroke with the gases discharging through the exhaust ports and the fuel being compressed in the crankcase and fuel feed conduit.

Fig. 3 is a view similar to Fig. 1 showing the inlet port to the cylinder uncovered by the piston and the compressed fuel entering the cylinder from the fuel feed conduit.

Fig. 4 is a plan view of the preferred form of rotary valve plug means of the invention.

Fig. 5 is an isometric View of the device shown in Fig.4. 1

Fig. 6 is a plan view of the preferred form of sleeve bearing for encircling the crankshaft.

Fig. 7 is a view in section on line 7-7 of Fig. 1.

Fig. 8 is a similar view in section on line 88 of Fig. 3, and

Fig. 9 is a side elevation of the preferred form of cylinder used in the invention.

In the drawings the two cycle, internal combustion engine 20 includes a single cylinder 21, a piston 22 and a crankcase 23. The cylinder 21 includes a head 24 and a glow plug 25, the inside face 26 of the cylinder head being tapered to match the tapered baffle 27 of the piston 22. The bottom 28 of cylinder 21 is open and suitable cooling fins 29 are provided around the cylinder.

As best shown in Fig. 9, the cylindrical wall 31 of cylinder 21 is apertured for nearly one third of its circumference to provide a fuel inlet port 32 at the front of the cylinder of relatively large area. The wall 31 also includes a pair of apertures each nearly equal in Width to one third the cylinder circumference, at the sides and rear of the cylinder, :to provide dual exhaust ports 33 and 34. The total area of exhaustv ports 33 and 34 is greater than the area of inlet port 32 and the exhaust ports are at a slightly higher level than the inlet port 32 to assure gas exhaustion before fuel feeding. Three narrow webs such as at 35 and 36 are thus provided in wall 31 each spaced apart and reducing the frictional resistance of the wall to the piston 22. I

The piston 22 includes a wrist pin 37 for a connecting rod 38, the rod 38 being connected to the crank pin 39.

The crankcase 23 is provided with a crank shaft bore 41 at the front thereof and leading into the base 42 of the crankcase compression chamber 43. A fuel feeding or supply conduit 44 extends up the front and outside of cylinder '21 and connects the fuel inlet port 32 with a fuel outlet port 45 at the bore 41. Conduit 44 is of relatively wide area of cross section and forms the upper part of the compression chamber 43, thereby allowing the fuel compressed by the descending stroke of piston 22 to concentrate close to inlet port 32 in conduit 44 rather than in the base 42, as in certain engines now in use..

Preferably an opening 46, coaxial with bore 41, is provided in crankcase 23 and filled with a detachable filler plug 47 thereby fillingadditional space in the base 42 of chamber 43 to further reduce the volume thereof.

Closely spaced to the fuel outlet port 45 and preferably also in the upper quadrant of bore 41 at the front of the engine is the fuel inlet port 50. Fuel inlet port Sil is at the terminal end of a fuel and air inlet conduit Sll formed in crankcase 23. Conduit 51 includes a fuel supply connection 52 to a source of fuel and the air and fuel are supplied thereby to the engine all in a well known manner. Inlet port 50 and outlet port of bore 41 are spaced apart by a web of material 53 and preferably inlet' port is of greater area than outlet port 45.

A crankshaft 55 is rotatably mounted in bore 4.1 and is preferably cylindrical in outline and of solid material. Crank shaft 55 is tapered at 56, the tapered portion 56 engaging a tapered seat 57 in a nut 58. Shaft 55 includes threads 59 at its front terminal end for a propeller or a power connection of any desired type. A crank disc 60 is provided on shaft 55 and carries the crank pin 39. Disc 60 is preferably bevelled at 61 at an angle of about 60 at its front edge.

The unitary, rotary valve plug means of the invention is achieved by the formation of a fuel passage, or valve port, 62 in the crank shaft 55. As shown, the shaft 55 is solid and the passage 62 extends axially therealong in the form of a deep groove with an arcuate bottom 63 and high side walls such as at 64 and 65. The ends 66 and 67 of passage 62 are dead ends the passage having the elongated opening 63 opposite to the integral wall 69.

With each revolution of crank shaft 55 the passage 62 connects the fuel inlet port 50 with the fuel outlet port 45 adjacent thereto and admits fuel into the upper portion of the crankcase compression chamber 43 at fuel eed conduit 44, as shown in Fig. 1. Thisis synchronized with the up stroke of piston 22 so that fuel is sucked into the entire chamber 43. Upon explosion of the fuel in cylinder 21, the piston 22 descends compressing the fuel in chamber 43, and rotating passage 62 of shaft 55 to closed position, thus preventing escape of fuel. As shown in Fig. 2 the entire bore 41 is sealed off by shaft 55 to eliminate the bore and shaft from the displacement volume of the chamber. Also in Fig. 2 the exhaust ports 33 and 34 are just being uncovered by piston 22 discharge the products of combustion. in Fig. 3 the piston 22 is in a low position where it uncovers the cylinder inlet port 32 to admit the fuel compressed in chamber 43 and conduit 44 into the cylinder.

Preferably the bore 41 is lined by a fixed bearing sleeve 72 of thin material and provided with an inlet aperture 73 corresponding to port 50 and an outlet aperture 74 corresponding to outlet port 45. As best shown in Fig. 6 the aperture 73 is larger in area than aperture 74 and the apertures are of oblong shape with rounded corners to increase the area thereof. V

It should be noted that the U-shaped groove or recess which forms passage 62 has no top wall but only bottom and side walls since the hearing, or the bore, serves to close the top opening. much used in the art, there is both a bottom wall and a top Wall with the top wall being perforated to admit fuel into the centre of the shaft. By grooving a solid shaft, as in this invention, the thickness of one wall is eliminated and the passage increased correspondingly in area of cross section. 7

It is preferred that the passage, or valve port 62 have a rectangular or oblong opening 68, with rounded corners as shown in Fig. 4. The area of the opening 68, correspondingly reduces the area of shaft 55 in contact with the bearing 72, thereby reducing frictional shaft resistance to rotation and improving efliciency of the engine.

I claim:

1. In a one cylinder, two cycle, internal combustion engine having a cylinder, a piston and a crankcase with a crank shaft bore the combination of a fuel inlet port in said housing connecting said crank shaft bore to a source of fuel; a fuel supply conduit in said housing, connecting said cylinder and crankcase to said bore and having a fuel outlet port at a spaced distance from said inlet port at said bore and a crank shaft rotatable in said bore and operably connected to said piston, said crank shaft forming unitary, rotary, valve plug means, including a valve port with opposite dead ends, adapted to connect said inlet and outlet ports in one angular position of said shaft and to plug said bore and disconnect said inlet and outlet ports in another angular position of said shaft during each rotation thereof.

2. A combination as specified in claim 1 wherein said crank shaft is solid except for a fuel passage intermediate of the length thereof, constituting the valve port of said rotary valve plug means.

3. A combination as specified in claim 1 wherein said inlet and outlet ports are closely spaced to, and aligned with each other, in the upper quadrant of said bore and said crank shaft includes an axially extending circumferential recess connecting said ports together when in angular registration therewith and constituting the valve port of said rotary valve plug means.

4. Acombination as specified in claim 1 wherein said crank shaft is solid and cylindrical except for an axially extending, straight groove in the curved surface thereof, connecting said ports together when in registration therewith and constituting the valve port of said rotary valve plug means.

5. A combination as specified in claim 1 wherein said crank shaft is solid except for an elongated, arcuate recess intermediate of the length thereof adapted to connect said ports together once in each revolution thereof for admitting fuel to said crank case, and having a single opening of generally oblong configuration.

6. A one cylinder, two cycle, internal combustion engine comprising a combustion cylinder having inlet and exhaust ports; a piston slideable in said cylinder and having a connecting rod; a crankcase having a crank shaft bore leading into a compression chamber, a fuel feed conduit leading from said bore and chamber up the front 40 of said cylinder to said cylinder inlet port, and a fuel intake conduit leading from a source of fuel to said crank shaft bore, proximate said fuel feed conduit, and rotary valve plug means comprising a solid, cylindrical crank shaft rotatable in said bore and operably connected to said connecting rod, said crank shaft having an arcuate, axially extending, dead-end, groove intermediate thereof adapted to connect said fuel intake conduit and said fuel feed conduit once with each revolution of said crank shaft but being adapted to sail off said bore during the remainder of each revolution thereof.

With a hollow shaft such as.

7. A combination as specified in claim 1 wherein said valve port defines a single oblong opening with rounded corners and said crank shaft bore is lined with a hollow tubular bearing having a pair of longitudinally spaced oblong apertures with rounded corners registering with, and coextensive in area with, said fuel inlet and fuel outlet ports.

References Cited in the file of this patent UNITED STATES PATENTS 

